[core] comment out unused part of http_etag_remix
[core] comment out unused part of http_etag_remix

note: etag buffer etag->ptr might be NULL (etag->used = etag->sze = 0)
so buffer will need to be extended, not truncated, in that case.
buffer_string_set_length() is typically used to truncate strings.

lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4,lighttpd/lighttpd1.4,lighttpd/lighttpd1.4,gstrauss/lighttpd1.4